Test layers on one engine and share selection and shader helpers

Layer display tests no longer re-check Cesium primitives in every layer:
they run on the fake engine, and one Cesium translation check per ground
kind lives in the Cesium engine's ground tests. Their harnesses are shared,
and the fake-engine, Cesium-engine and flights tests that repeated the
contract suite are gone, 340 tests in all.

The press-travel measurement is shared by the selection dispatcher and
CCTV, which loses its ScreenSpaceEventHandler shim and world-click module.
ALPR, installations and bikeshare share one selection keeper and selected
marker write. Layers with their own click rules keep their handlers.

Navara's pulse is a class like the ground pass, the ground and imagery
passes share the surface uniforms, and the colour, log-depth and occlusion
GLSL lives in one chunk module, each caller keeping its depth bias. The
ground suite runs inside the contract suite (--only=ground:), and fixture
and script names say what they test.

Behaviour is unchanged on both engines.

scripts/qa-browserEvidence.mjs

@@ -47,7 +47,11 @@ export function isExpectedPreviewSetupError(
 
 // The runtime evidence gate shares one strict runtime verdict across its main page and
 // every share-link page. Response diagnostics never retain query credentials.
-export function watchW1Page(page, report, { name, preview = false, baseUrl }) {
+export function watchBrowserPage(
+  page,
+  report,
+  { name, preview = false, baseUrl },
+) {
   const errors = (report.browserErrors ??= []);
   report.expectedPreviewErrors ??= [];
   report.failedResponses ??= [];